Antifreeze composition



States I] atent Patented Jan. 2, 1962 No Drawing.

This invention relates to novel corrosion inhibited single phasepermanent antifreeze compositions and to aqueous solutions thereof. Theinvention also concerns a method of producing the novel antifreezes andtheir aqueous solutions. In addition, the invention covers a method ofpreventing corrosion of metals which come in contact with suchcompositions.

In antifreeze mixtures the freezing point depressant is essentially oneof two types, namely, non-permanent and permanent. The non-permanentfreezing point depressant is a water-miscible, low boiling monohydroxyalcohol such as methyl alcohol, ethyl alcohol, propyl alcohol, andmixtures thereof. The permanent type antifreezes to which this inventionis directed contain as a freezing point depressant a water-soluble, highboiling polyhydroxy alcohol such as ethylene glycol, propylene glycols,butylene glycols, and mixtures thereof.

It is well known that both uninhibited permanent and non-permanent typeantifreezes and aqueous solutions thereof cause serious corrosion ofmetals during service.

These antifreeze mixtures promote corrosion of brass,

copper, solder, steel, iron and aluminum in heat exchange apparatus suchas the cooling systems of internal combustion engines.

A large number of corrosion inhibitors and combinations thereof havebeen employed in the prior art to inhibit the corrosive action ofnornpermanent and permanent type antifreezes. The antifreezes having theinhibitors dissolved only in the freezing point depressant and withoutany oil layer are known as single-phase antifreezes; and those whichhave inhibitors dissolved in a separate oil layer are known as the twophase antifreezesf Although many of the prior art inhibited antifreezesare generally satisfactory, they.are often deficient in one or moreaspects. For example, they may, when used as a coolant in automobilecooling systems deteriorate the rubber radiator hose, creep, foam and/or fail to provide adequate corrosion protection for one or more metalsforming such cooling systems. Furthermore, those of the two phase typecannot be shipped in bulk because of the difliculty of recovering theproduct with the proper proportion of oil and glycol.

An object of this invention is to provide new antifreeze compositionsand aqueous solutions thereof which afford superior corrosion protectionto metalsnormally found in heat'exchange apparatus. Another object istoprovide an antifreeze which is non-foaming, resistant to creep and.

does not deteriorate rubber. Still another object is to provide anantifreeze which is of low cost and of simple preparation, and which maybe shipped in large volume bulk containers such as drums or tank cars.

In accordance with this invention and the objects cipita-ted oxidationproducts such as dibenzothiazole di-.

vention as the freezing point depressant component are any of thewater-soluble liquid glycols such as ethylene glycol, propylene glycols,butylene glycols, diethylene glycols, and the like. The freezing pointdepressant should generally constitute between about 10 and volume(vol.) percent of the novel antifreeze compositions. A preferred glycolis ethylene glycol, which as sold commercially often contains a smallamount up to 10% by weight of diethylene glycol. The term ethyleneglycol as used herein is intended to read either on the pure orcommercial compound. a

I include within the definition of magnesium tetraborate, the hydrous aswell as the anhydrous forms thereof. The quantity of magnesiumtetraborate employed in the novel antifreezes should generally be about.01 and 5% by weight (wt.) based on the glycol. Preferably magnesiumtetraborate concentrations are between about 0.5 and 3 wt. percent.

Several specific examples of the alkali metal rnercaptobenzothiazolescontemplated herein are sodium mercaptobenzothiazole and potassiummercaptobenzothiazole. The quantity of alkali metalmercaptobenzothiazole employed should generally be between about 0.0001and 1%, preferablybetween about .01 and 0.5% by Weight based on theglycol. The preferred alkali metal mercaptobenzothiazole is sodiummercaptobenzothiazole.

Among the metals to be protected by the disclosed novel antifreezecompositions are brass, copper, solder, steel, iron and aluminum.

Water may be combined with the antifreezes of this invention in any andall proportions to form the aqueous antifreeze solutions thereof. Whenaqueous solutions of the novel antifreezes are to be used as coolants inautomotive cooling systems, the water-miscible liquid glycol shouldgenerally constitute at least about 10 vol. percent, preferably betweenabout 20 and 90 vol. percent, of the aqueous antifreeze solution.

It is to be noted the freezing point of the aqueous glycol coolants issubstantially determined by the quantity of glycol therein. For example,a minimum. freezing point of approximately -60 F. is obtained with about60% ethylene glycol by volume. Further increase or de-' crease in theethylene glycol concentration raises the freezing point.

In the preparation of our novel antifreeze composi' tions and theaqueous solutions thereof, the magnesium tetraborate is convenientlyformed in situ by adding boric acid and magnesium oxide (MgO) in a'molratio of between about 3.511 and 45:1, preferably 4:1, to a watersoluble liquid glycol with stirring, and heating the mix-- ture tobetween about 150 to 250 F. with continued stirring until all evidenceof milkiness" has disappeared.

A small amount of Water is also formed in this reaction,

but it is not an essential ingredient of the antifreeze con centrate asfar as corrosion inhibition and coolant prop erties are concerned. Theresultant solution is then cooled, preferably to below about 'F., andthe alkali metal mercap'tobenzothiazole is added as a solid or anaqueous solution with'stirring and the stirring is continued untilvisual observation reveals a homogeneous product.-

in the antifreeze. Also, it is desirable to filter the aque-.

ous alkali metal mercaptobenzothiazole before adding to the antifreezein order to insure the removal of any presulfide. Dibenzothiazoledisulfide although not adversely affecting the chemical and physicalproperties of the novel antifreezes does cause a haze therein whichv maypromote consumer resistance to the product.

If desired, the above homogeneous antifreeze products may be diluted bymixing with portions t'o'form aqueous solutions thereof.

The following examples serve to illustrate my invention in greater d etailz the "novel antifreezecomposition'sj I I I I I To 96 .48 pounds (lbsf J "of c'ornmerlc 1 grade ethylene glycol; whichwas continuouslystirred duriti'g'the entire tim'e of theantifree'ze pi paranaaitneie wasmass-172 lbs. of boric a'cid an'd the resultant' miiiturei'Was heated;

This'examp'le illustrates the method at; ,nr'eparationjof When atempratu'r'e or 200 was freach d f magnesium oXi'de Was adde'd to" ithe" Stirred and the mixture temperature as'heId 'ia'tfZ'OOf all traceof milkinessnhereinhad disappeared. The resulting solution Wasthencooled to 1 00 F; i and 0.78 lb; of "a'fi1tered '50% by" weight solutionof sodiuni-inercap} addedfii Stir'ring was' continued untiY'a'clearhomogeneous roductwas formed. The'precdingquantities produced 10.6gallons of final product.

The final -i jrodlictRivas" of 1th *fo llowi g Co I Weightp Ingredients-i e Ethylene"glycol Magnesium tetraborate ISodium'-mercaptobenzothiazole ercent- 96:48

his. to be notedthat-the use:of water in the above procedure is not anessenti al for the formulation .of :the' novel antifreeze. l1 a it W EXAMPLE 11:.

This eXample illustrates theg;corrosion inhibition grefiece. tiveness ofthe antifreeze 1 compositions" 'of this invention. The: corrosion .testemployed and which 1 is t describedv L t P directly below-sunnimes;conditions; under-Wh1ch corr0-,

(by: We ht) c Q i e- 0n c nc ntr o -s .The air 1 ou l tube .isconnectedto: aywater cooled; condenser sand the. joined inlet; tubes,.are;connected,-,to a compressed air sou -ev heapp nzt pvo the es-slosedwi h n w:

i of steelpc-astiron; and, so1der., .Although; my :novel antirolled corkthrough which is passedt-a; glass rod ending in 'ZL -hQOK fIQIlI i whichiawbundle eoi test metal strip zi suspended. by a Nichromewire. ,The,test bundie'v com pr e de n "a ds si ed-r. -t s .metala t ps f: copperbrass solder,--cast 1ron,rstee l, and cast aluminum having aknownsurface arearemovably mounted, on;a brassbolt;eand:spacedfwith;.,stainless ste'elwasher's; The boltjisl tightenedwith anb'rassh-nut to'holdwthettest metal strips: rigid; Thisarrangement galvanically couplesthe individualmetal strips :to one-anotherjrgThe surface area of j the's e test" metals are inapproximately the same rel ative proportion to one another asthey"wouldfbe is refiresent ative' automotive "I'c ooling sysitem'. The ratio-oftst-Iine tal surface in i lant' i sI'al soapiirokimatelyf i fs i ases an, lThesla mmer r. placed, in an, on Jbat h} ma ntained the air inle ubesf e est-15.1 -znii ili iil( ns-T)11 st. min t T e. w s-, rsv ouslysctub sdi frseoi. y

water in any and all protest solution through; II

carbon dioxide by passing it through a solution of wt: percentsadismhyaroxid'amwater; The cell is main test metal strip :Antnreezecomponent s- 2.5 Composition of antifreeze component, weight percent: 4Ethylene glycol... g 96.48 Magnesium tetrab'or 1.26sodium'me'roaptobenzoth 014te ts thegantifreeze to by yolume containsa3200 ;p.p.m.;

tained in the oil bath for afi'period of 161 hours (hrs) whereupon thetest bundle is removed. Each test metal strip is freed of corrosionproducts by scrubbing with a household abrasiveieleaner and a's'oft'cloth and then successively iinsed" indistilld water and 'acetonef 1 Each 'then dried ancifreweighedwith the weightd'oss'b'ein.caleiilated on e-ease of milligrams lost per square deciineter of'ori'ginal surface area of the testst-riplmg sq. t

Composition of test; solution, volg n'erceiitz Water component (2001). m

. .Finnlv I I Reserve all 1' ty to pH Initial F n t Coragsiorrloss oftest 'strips, 'mg'./sq. dm.

Corrosion loss for cach'ine is. r

As can be seen from the above tableg novelhin-j hibited;antifreeze}Besubstantially reduces the corrosion This time; nhist'r'ft s'th'eisyner gistic,,lcorrosion. i'ni nibitgr actionft r "solder, steel,and ifas iron ofv the. magarn; ,rnetal, 'm ican b zqhe ov'el antifreezecompositions t' LCorrosion loss for each metal based on average weightloss/sq. dm. of 4 es s.

Inspection of the above table shows the magnesium tetraborate-alkalimetal mercaptobenzothiazole combination in the novel antifreezerepresentative acts synergistically to reduce corrosion of solder, steeland cast iron. This synergistic action is particularly clear in the caseof solder. When only one member of the inhibitor combination isemployed, the corrosion loss of solder is higher than with anuninhibited ethylene glycol antifreeze, yet when both are employed, thecorrosion loss of solder is substantially lower.

EXAMPLE IV This example illustrates the superiority corrosion-wise ofthe novel antifreeze compositions over an antifreeze taught in the priorart.

Two antifreeze formulations were subjected to the corrosion testdescribed in Example II and were respectivelydesignated as antifreeze Gand antifreeze H. Antifreeze G is 'a representative of the prior artantifreeze and antifreezeH is a representative of the antifreezecompositions of this invention.

The test data and results are reported below in Table III. Also the pHand reserve alkalinity of the initial and final test solutions arementioned.

Table III Description Antifreeze Antifreeze Composition of the testsolution, vol. percent:

Water component (200 p.p.m. Cl-) 75 75 Antifreeze component 25 25Composition of antifreeze component, weight percent:

Ethylene glycol Magnesium tctraborate. Sodium tetraborate Sodtiummercaptobenzothiazole Tnitial 9 Final 0 Reserve alkalinity to pH of 5.5:

Initial 7 Final .4

Corrosion loss of test strips, mgJsq. dm.:

Brass 18 17 Copper 11 12 Solder 78 42 SteeL. 101 24 Cast iron 27 14 Castaluminum 185 78 1 Corrosion loss for each metal based on average weightloss/sq. dm. of 4 sts.

As can be seen in the above table, my novel antifreeze compositionsrepresented by antifreeze H provide superior corrosion protection to allthe tested metals with the possible exception of copper.

6 EXAMPLE IV This example illustrates the desirable foam resistantproperties of the novel antifreeze compositions and their superioritywith respect to foam resistance over a prior art antifreeze as well astheir superiority over an uninhibited glycol formulation.

The foam test procedure employed consists of placing 250 cc. of a 40% byvolume antifreeze in distilled water in a clean 800 ml. beaker andstirring the beaker contents with an electric mixer of the householdvariety operated at a speed of 1000 rpm. for a second period whilemaintaining the test solution temperature at F. At the instant the mixeris cut off, the foam height and the foam callapse time are measured. Thefoam collapse time is the interval between the cutting off of the mixerand the appearance of the first stable opening in the foam layer.

In addition to the above test, a modified foam test was employed. It isidentical to the above procedure except a foam producing agent was addedto the aqueous test solutions to form solutions having a foam producingagent content of 5 and 10% by volume. The composition of the foamproducing agent employed, designatedv as agent X, .is as follows:

Ingredients: Weight percent Sodium sulfonate oil mixture 16.0 Gum rosin4.2 Naphthenic acid 7.1

- Sodium hydroxide (49 Wt. percent in water) 2.0

Ethylene glycol monohutyl ether 1.0 Water 0.9 Lubricating oil (SayboltUniversal viscosity of 70 seconds at '100'F.) 68.8

Table IV Anti- Anti- Anti- Desoription freeze freeze freeze I I KComposition of test solution, vol. percent:

Water component (distilled) 60 60 60 Antifreeze component 40 40 40Composition of antifreeze component, weight percent:

Ethylene glycol 96.48 96.48 96 48 Magnesium tetraborate l 26 Sodiumtetraborate 1. 26 Sodium mercaptobenzothiazole O. 13 0. 13 Water 3. 522.13 2. 13 Foam height, inches:

Test solution Me 0 Test solution +5 vol. percent agent X 4% 3% 0 Testsolution +10 vol. percent agent X... 4 1; 3 0 Foam collapse time,seconds:

'Iest solution 0 2 0 Test solution +5 vol. percent agent X. 600 142 0Test solution +10 vol. percent agent X. 600 82 0 From an inspection ofthe results reported in the above Table IV, it is seen that my novelantifreeze composition represented by antifreeze K does not foam andprevents foaming even in the presence of a foam producing agent. Theprior art antifreeze represented by antifreeze J undesirably foams withor without a foam producing agent. The uninhibited glycol represented byantifreeze I does not have reserve foam resisting properties.

In an extensive field test conducted on my novel antifreeze compositionsin automotive engines no deterioration of rubber radiator hosing wasfound nor was any excessive creeping by the antifreezes observed.

Obviously, many modifications and variations of the invention ashereinbefore' set'forthifnay be made Without departing from the, spiritand scope thereof and therefore; only such limit ationsfshould posed'a"dic a t edl in the appended i claim; a

1. 'An antifreeze com'positlo waten consisting, essentially oi?glycoL-betweenaboutjQOl and 5%" nesium tet'raborateaiid between jabweight ofan alkali metal merciapto v.2. \Ani'afitifreeZe composition adawater consistingessentiallyfofa wat col atweea ab ut 0.5 f'and'3'%j bytetr abo'ratejiand between about v ofan alkali nietalmetcmitobenZ hi j3, AII 3II'[ifiB EZ composition 1" ace 2, wherein said glycol isethylene'lgly metal ,mercaptobenzothiazole,fis sodin thiazole 1 f T -1 nnt zej 9 i P $ll 9n Pi between about l0.and lOQ% A soluble il iquidglycoLsolution on .01 and byfwe ight of mag'n betweenabout .OOOI and 1%by yeightt-of iafialkal mercaptobenzothiazole, the remainder of said ction'being 'water. I

5. An antifreezecomposition eonsisting essentially of between about- 10and 100% by-yolume' of soluble liquid -glyc0l solution containing-hem nabout 0,5 and 3%- by weight "of magnesium tetrabor and between about .01and 0 .5'%b y Weight of-analkali mercaptobenzothiazole; ;theremainde1---of-- said tion being water.

6'. An'antifreeze composition'inaecordance with claim 5 w in s id y o ie hylen a ly iol anisa q alk metal, mereaptobenzothiazole; is 5 sodiummercapt thiazole.

7. .A m hod; of p o i g a antit ee 2 29 P s mi s boric a d: ndm ne miwde n2 amolratiqof betweenaboutij: an d 4.5 in a ate r 4Q soluble liquidglycol. at between @bOulZ L5Q and 0; untilthe resultantv solution,is-;sub stan tially clear, subsequently reducing said solution;tempeatui e ;to below about 120 F., and thenmixing said resultant solutionwith an alkali metal mercaptobnzothiazole, the proportions of saidglycol, said boric a ci dQsaid magnesium oxide and said alkali metalmercaptobenzothiazole being adjusted in a manner to form saidcomposition containing between about .01 and 5% by weight ofmagnesiumtetraborate and between about ,OOQllahdflfZ byweight of saidalkali metalmercaptobe thiaio v 8. A method in aec'ordancewitli"claini7' whereiproportions of said glycol, said boric acid, said magnesium oxide andsaid alkali metal mercapto'benizotliia z'ole aielad- 5 jus'tedtoformsaid composition"-'coiitaining between bout posi n-learntsubsequently reducing fsaid solution f'tempeiatu:

10. A method in accordan'c'ewithClaim 7 wh'eife'i fsalid alkali metalmercapto'benzothiazole"is addedi as a lt'e'red aqtleousf-isolution. V Vi v 11. A method of producing-"an aqueoiis antifreeZe-oonfi Tmg mix sbqiq asid oxide in; a m1 I I w lw l b ca;l quids-gly o i at ill :z ho 1 W250 E, until the resultant solution substantially eleaf's; .bel w about112i) Rand then mixing with s'aid' r'esulta'n tiil an" alkalimetalineficaptobjenzethiaiolefancl w proportions of said glycol, saidbor'ieacidjsaid magne din oxide and said-alkali meta-lmercaptobenzothiazole;being adjusted; in a manner to: form'saidcomposition eon'tai'ning betweenabout l0 andl'OO%"by" oluine of s dglycol, etwnl'bb 11 1 1 2 WWi t offa W and bet Ween'about 10081 mamaweight tet'r'aborate 05% by Weight efis a d alkalimstal and between .01and mercaptobenzothiaz ole, said percent by weight of said magnesiumtetraborate andsaid allcali metal mercaptowater- Referenc te r t e fileof t Paten 7 I w-UNI'TED STATES PATENTS 2,373,510, Apt-V170, .1 4

2,534,030 Kellen. d 2,765,278 Holter 956 "2,815,328""' Green

1. AN ANTIFREEZE COMPOSITION ADAPTED TO BE ADDED TO WATER CONSISTINGESSENTIALLY OF A WATER-SOLUBLE LIQUID GLYCOL, BETWEEN ABOUT .01 AND 5%BY WEIGHT OF MAGNESIUM TETRABORATE AND BETWEEN ABOUT .0001 TO 1% BYWEIGHT OF AN ALKALI METAL MERCAPTOBENZOTHIAZOLE.